There's a good chance OPEC, Russia and other producers could deepen production cuts when they strike a new deal later this month, according to Citigroup.

Ed Morse, global head of commodities research at Citigroup, said he sees a 60 to 70 percent chance of the 1.8 million barrels per day of current cuts becoming larger as the producer group extends their deal to March 2018.

He said it is possible they could cut another 300,000 to 500,000 barrels per day, and Saudi Arabia would have to contribute the lion's share. OPEC, Russia and other oil producers first agreed to a six-month production cut in December.

Earlier Monday, Saudi Arabia energy minister Khalid al-Falih and Russia energy minister Alexander Novak said they would like to extend the current agreement by 9 months and that they would discuss it with other producers. OPEC is expected to approve an extension of the deal at its May 25 meeting.

"I wouldn't be surprised if they're working on a deeper cut," said Morse. He said the fact that they are discussing extending the deal does, in essence, make the cut bigger than if it had been extended by only six months, as expected.